Field of the Invention
This invention relates to systems and methods for increasing the data availability of logical volumes.
Background of the Invention
In the context of computer operating systems, a “volume” is a fixed amount of storage on disk, tape, or some other storage device. The term “volume” may be used to refer to either a “physical volume” or “logical volume.” A “physical volume” may refer to a single physical storage device, such as a hard disk drive, solid state drive, optical disk (e.g., CD, DVD, etc.), tape cartridge, or the like. A “logical volume,” by contrast, may not map directly to a single physical storage device. For example, a logical volume may span multiple physical volumes or a physical volume may be divided up into multiple logical volumes (e.g., partitions). Storage virtualization software may map storage elements in a logical volume to their actual physical locations on underlying physical storage devices. From the point of view of an operating system or application, a logical volume may appear to be a single physical volume.
With the advent of very large logical volumes such as Extended Addressable Volumes (EAVs) in the z/OS operating system, operations at a volume level can take a significant amount of time due to the increased amount of storage space in these volumes. This can significantly impact applications and users trying to access the logical volume when the logical volume needs to be serialized (i.e., locked while operations on the volume take place). For operations such as data defragmentation, data consolidation, and/or data rebalancing, where a lock may be issued against the entire volume (and more particularly against the volume table of contents (VTOC) associated with the volume), the volume may be inaccessible to other applications and users while the operations take place.
In view of the foregoing, what are needed are systems and methods to increase the data availability of volumes, particularly very large volumes such as Extended Addressable Volumes, while data reorganization operations are taking place. Ideally, such systems and methods will reduce or minimize the performance impacts associated with data reorganization operations.